Polymerase Chain Reaction (PCR) is one of the most widely used techniques in molecular biology, enabling researchers to amplify specific DNA sequences from minimal starting material. Whether used in molecular cloning, pathogen detection, genotyping, sequencing library preparation, or diagnostic assay development, PCR relies on the precise coordination of several essential components, including template DNA, primers, DNA polymerase, magnesium ions, and nucleotide substrates.
Among these components, deoxynucleoside triphosphates (dNTPs) play a fundamental role because they provide the building blocks required for new DNA synthesis.
During PCR amplification, DNA polymerase cannot create new DNA strands without dNTPs. The enzyme extends primers by incorporating four nucleotide substrates:
- dATP (deoxyadenosine triphosphate)
- dCTP (deoxycytidine triphosphate)
- dGTP (deoxyguanosine triphosphate)
- dTTP (deoxythymidine triphosphate)
Together, these four molecules form the complete substrate set required for accurate DNA replication.
The concentration and quality of dNTPs directly influence PCR performance. An insufficient dNTP concentration may limit DNA synthesis and reduce amplification yield, while excessive dNTP levels can decrease specificity by affecting magnesium availability and increasing nonspecific amplification.
Therefore, selecting the appropriate dNTP concentration and using high-quality nucleotide reagents are critical steps for achieving efficient, reproducible PCR results.
What Are dNTPs?
dNTPs, or deoxynucleoside triphosphates, are nucleotide molecules that serve as the substrates for DNA synthesis.
Each dNTP molecule contains three major components:
- A nitrogenous base
- A deoxyribose sugar
- Three phosphate groups
The nitrogenous base determines the identity of each nucleotide:
- Adenine (A)
- Cytosine (C)
- Guanine (G)
- Thymine (T)
The four canonical dNTPs—dATP, dCTP, dGTP, and dTTP—provide the information-carrying units required to construct DNA molecules.
Unlike ribonucleoside triphosphates (NTPs), which are used for RNA synthesis, dNTPs contain a deoxyribose sugar lacking the 2'-hydroxyl group found in RNA nucleotides. This structural difference allows DNA polymerases to specifically recognize and incorporate dNTPs during DNA synthesis.
What Is the Role of dNTPs in PCR?
The primary function of dNTPs in PCR is to provide the raw materials required for DNA polymerase-mediated DNA extension.
During each PCR cycle, the reaction proceeds through three major steps:
1. Denaturation
The double-stranded DNA template is heated to separate the two DNA strands.
2. Annealing
PCR primers bind to complementary sequences on the single-stranded DNA templates.
3. Extension
DNA polymerase extends the primers by adding complementary dNTPs to synthesize new DNA strands.
For example:
- If the template contains adenine (A), DNA polymerase incorporates thymine-containing dNTP (dTTP).
- If the template contains cytosine (C), DNA polymerase incorporates guanine-containing dNTP (dGTP).
Each nucleotide addition forms a phosphodiester bond between the growing DNA strand and the incoming dNTP.
During this process, the terminal phosphate groups of dNTPs provide the chemical energy required for DNA polymerization. The release of pyrophosphate (PPi) drives the reaction forward and allows continuous DNA strand extension.
Without dNTPs, DNA polymerase has no substrate to incorporate, meaning PCR amplification cannot occur.
What Is the Purpose of dNTPs in PCR?
The purpose of dNTPs in PCR is to enable DNA polymerase to synthesize new DNA copies of the target sequence.
Specifically, dNTPs serve three essential functions:
Providing DNA Building Blocks
PCR generates millions to billions of copies of a target DNA fragment. Each new DNA molecule requires a continuous supply of dNTP molecules as construction materials.
Supporting Accurate DNA Replication
The balance of dATP, dCTP, dGTP, and dTTP ensures that DNA polymerase can accurately copy the template sequence.
An unbalanced nucleotide pool may increase incorporation errors and reduce amplification reliability.
Driving DNA Polymerization
The high-energy phosphate bonds in dNTPs provide the energy needed for DNA strand extension.
Therefore, dNTPs are not simply raw materials—they are active participants in the biochemical process that enables PCR amplification.
The Importance of dNTP Quality in PCR
While dNTP concentration is important, nucleotide quality is equally critical.
PCR reactions are highly sensitive to contaminants that may interfere with DNA polymerase activity or compromise downstream analysis.
Low-quality dNTP preparations may contain:
Nucleotide Degradation Products
Hydrolyzed nucleotides such as diphosphates (dNDPs) or monophosphates (dNMPs) cannot support efficient DNA synthesis and may reduce reaction efficiency.
Nuclease Contamination
DNase contamination can degrade DNA templates, while RNase contamination may affect workflows involving RNA-derived templates such as RT-PCR.
Incorrect Concentration
Variation between batches can affect PCR optimization and lead to inconsistent amplification results.
For this reason, researchers commonly select dNTP reagents with:
- High HPLC purity
- Accurate concentration measurement
- Low nuclease contamination
- Reliable lot-to-lot consistency
High-quality dNTPs help improve PCR reproducibility, especially in demanding applications such as quantitative PCR, multiplex PCR, and molecular diagnostics.
What Is the Optimal dNTP Concentration for PCR?
One of the most important factors affecting PCR performance is the concentration of dNTPs in the reaction mixture.
Although the optimal concentration depends on the DNA polymerase, template characteristics, and assay design, most conventional PCR reactions use a final concentration of approximately:
0.2 mM of each dNTP
This means the reaction typically contains:
- 0.2 mM dATP
- 0.2 mM dCTP
- 0.2 mM dGTP
- 0.2 mM dTTP
resulting in a total dNTP concentration of 0.8 mM.
This concentration range provides sufficient nucleotide availability for DNA synthesis while maintaining a balance between amplification efficiency and specificity.
For many standard PCR applications, commercially available 10 mM dNTP mixes are diluted appropriately to achieve the desired final concentration, simplifying reaction setup and reducing preparation errors.
Why Does dNTP Concentration Matter in PCR?
The concentration of dNTPs directly affects the ability of DNA polymerase to synthesize new DNA strands.
An appropriate dNTP concentration ensures:
- Efficient primer extension
- High DNA yield
- Accurate nucleotide incorporation
- Reduced nonspecific amplification
However, PCR reactions involve a delicate balance between multiple components. Increasing dNTP concentration does not always improve amplification. In many cases, excessive nucleotide levels can negatively affect PCR performance.
Therefore, dNTP optimization is not about using the highest possible concentration—it is about finding the concentration that provides the best balance between efficiency, specificity, and fidelity.
What Happens If dNTP Concentration Is Too Low?
Insufficient dNTP concentration can limit DNA synthesis during PCR.
When nucleotide availability becomes a limiting factor, several problems may occur:
Reduced Amplification Yield
DNA polymerase requires a continuous supply of dNTP substrates to extend newly synthesized DNA strands. If dNTP levels are insufficient, amplification may slow down or stop prematurely.
Weak or Absent PCR Bands
In endpoint PCR, low dNTP concentrations may result in weak bands or complete amplification failure, especially when:
- The template concentration is low
- The target fragment is long
- The number of amplification cycles is limited
Reduced Sensitivity
For applications requiring high sensitivity, such as pathogen detection or rare mutation analysis, insufficient dNTP availability may reduce assay performance.
What Happens If dNTP Concentration Is Too High?
Although increasing dNTP concentration may appear beneficial, excessive dNTP levels can negatively affect PCR reactions.
Common problems associated with excessive dNTP concentration include:
Reduced PCR Specificity
High concentrations of dNTPs can promote nonspecific amplification by allowing DNA polymerase to extend incorrectly primed products.
This may lead to:
- Additional unexpected bands
- Higher background signals
- Reduced assay accuracy
Magnesium Ion Imbalance
dNTPs bind magnesium ions (Mg²⁺), which are essential cofactors for DNA polymerase activity.
When dNTP concentration increases excessively, more Mg²⁺ becomes unavailable for polymerase catalysis.
This can result in:
- Reduced polymerase activity
- Lower amplification efficiency
- Changes in primer-template interactions
Increased Error Rates
For some polymerases, particularly those lacking proofreading activity, excessive dNTP concentrations may contribute to reduced replication fidelity.
This is especially important for:
- Cloning applications
- Mutation analysis
- Synthetic biology workflows
Factors That Influence dNTP Optimization in PCR
Although 0.2 mM of each dNTP is a common starting point, optimal concentration depends on several experimental factors.
DNA Polymerase Selection
Different DNA polymerases have different requirements for nucleotide concentration.
For example:
- Standard Taq DNA polymerase generally performs well with conventional dNTP concentrations.
- High-fidelity polymerases may require optimized nucleotide levels to maximize accuracy.
- Specialized polymerases designed for difficult templates may tolerate different dNTP conditions.
Researchers should always consider the recommended reaction conditions provided by the polymerase manufacturer.
Amplicon Length
The size of the target DNA fragment can influence dNTP requirements.
Longer DNA fragments require more nucleotide incorporation events, meaning sufficient dNTP availability becomes increasingly important.
For long-range PCR, optimization of:
- dNTP concentration
- polymerase amount
- extension time
may improve amplification success.
GC Content and Template Complexity
GC-rich regions and structurally complex templates can present challenges during PCR amplification.
These targets may require optimization of multiple parameters, including:
- Annealing temperature
- Magnesium concentration
- Polymerase selection
- dNTP concentration
In some cases, specialized nucleotide formulations or modified nucleotides may improve amplification performance.
PCR Application Type
Different PCR workflows may require different dNTP considerations.
Conventional PCR
For routine DNA amplification, balanced dNTP mixes at standard concentrations are typically sufficient.
qPCR
Quantitative PCR requires highly consistent reaction conditions because small variations may affect fluorescence-based quantification.
High-purity dNTPs with accurate concentration are preferred to ensure reproducible Ct values.
Multiplex PCR
Multiplex assays amplify multiple targets simultaneously and are particularly sensitive to reaction balance.
Optimization of:
- dNTP concentration
- primer concentration
- magnesium concentration
may improve specificity and reduce unwanted products.
High-Fidelity PCR
For cloning, sequencing preparation, and synthetic biology applications, nucleotide quality and balanced concentration are critical to maintaining sequence accuracy.
How to Optimize dNTP Concentration in PCR
When PCR performance is not optimal, adjusting dNTP concentration can be part of a systematic optimization strategy.
A typical optimization workflow includes:
Start With Standard Conditions
Most PCR assays begin with:
- 0.2 mM each dNTP
- Recommended polymerase concentration
- Standard Mg²⁺ concentration
This provides a reliable baseline.
Test a Range of dNTP Concentrations
If optimization is required, researchers may evaluate different dNTP concentrations, such as:
- Lower concentration conditions
- Standard concentration conditions
- Higher concentration conditions
The best condition is determined by evaluating:
- Amplification yield
- Product specificity
- Background signal
- Reproducibility
Optimize dNTPs Together With Mg²⁺
Because dNTPs interact with magnesium ions, changing nucleotide concentration may require adjustment of Mg²⁺ levels.
An optimized balance between:
- dNTP concentration
- Mg²⁺ concentration
- DNA polymerase activity
is essential for efficient DNA synthesis.
Common Mistakes When Using dNTPs in PCR
Even when the correct nucleotide type is selected, several common mistakes can affect PCR performance.
Using Incorrect dNTP Concentration
Too little dNTP may limit amplification, while too much may reduce specificity.
Starting with the recommended concentration and optimizing only when necessary is usually the best approach.
Using Degraded dNTPs
Repeated freeze-thaw cycles or improper storage can gradually reduce nucleotide quality.
To maintain stability:
- Store dNTPs at recommended temperatures
- Avoid unnecessary freeze-thaw cycles
- Use properly aliquoted solutions when possible
Ignoring Nucleotide Purity
PCR sensitivity varies significantly depending on the application.
While standard PCR may tolerate minor variations, demanding workflows such as:
- qPCR
- sequencing
- molecular diagnostics
- cloning
require higher-quality dNTP reagents.
Assuming All dNTP Mixes Are Equivalent
Different dNTP products may vary in:
- Purity level
- Buffer composition
- Salt formulation
- Stability
- Quality control standards
Selecting a suitable nucleotide formulation can improve reproducibility and reduce troubleshooting time.
Choosing the Right dNTP Product for PCR
Selecting the correct dNTP product is not only about choosing the right nucleotide type. Researchers should also consider the formulation, purity level, and compatibility with their specific PCR workflow.
Different applications may require different nucleotide formats depending on the experimental objectives.
dNTP Mix vs Individual dNTPs: Which Should You Choose?
dNTP products are commonly available in two formats:
- dNTP mixes containing all four nucleotides
- Individual dNTP solutions containing separate nucleotides
Each format provides different advantages.
dNTP Mixes for Routine PCR
For most PCR applications, a balanced dNTP mix is the most convenient choice.
A standard dNTP mix contains:
- dATP
- dCTP
- dGTP
- dTTP
at equal concentrations, ensuring consistent nucleotide balance in every reaction.
Advantages of dNTP mixes include:
- Reduced pipetting steps
- Lower risk of preparation errors
- Improved experimental consistency
- Faster reaction setup
They are commonly used for:
- Conventional PCR
- Colony PCR
- qPCR
- RT-PCR
- DNA cloning
- Routine molecular biology workflows
For laboratories performing large numbers of PCR reactions, ready-to-use dNTP mixes can significantly simplify workflow management.
Individual dNTPs for Assay Development and Optimization
Individual dNTP solutions provide greater flexibility when researchers need precise control over nucleotide composition.
Separate dATP, dCTP, dGTP, and dTTP solutions allow researchers to:
- Adjust individual nucleotide concentrations
- Develop customized PCR systems
- Optimize specialized amplification protocols
- Evaluate polymerase performance
They are particularly useful for:
- New assay development
- Synthetic biology applications
- DNA engineering workflows
- Research requiring customized nucleotide ratios
Specialized dNTP Formulations for Advanced PCR Applications
Beyond standard dNTP mixes, many advanced PCR workflows require specialized nucleotide formulations.
dNTP/dUTP Mixes for Contamination Prevention
In molecular diagnostics and high-throughput PCR laboratories, carryover contamination is a major concern.
One widely used strategy replaces dTTP with dUTP.
The workflow typically combines:
- dUTP-containing nucleotide mixtures
- Uracil-DNA glycosylase (UDG)
During this process, previous PCR products containing uracil can be selectively degraded before amplification, reducing the risk of false-positive results.
dUTP-based systems are commonly used in:
- Molecular diagnostics
- Pathogen detection
- Clinical testing
- High-throughput PCR screening
Hotstart dNTP Formulations for Improved PCR Specificity
Some challenging PCR assays require enhanced control over nonspecific amplification.
Hotstart dNTP Mix is an innovative product in the field of PCR technology. It is a specially chemically modified deoxyribonucleotide that cannot participate in phosphodiester bond formation at room temperature. After heat activation, it converts to regular dNTPs, enabling participation in PCR amplification. This product significantly reduces non-specific amplification caused by non-specific annealing or primer dimers.
Combined with compatible HotStart polymerases, HotStart dNTP formulations can support:
- Multiplex PCR
- Low-copy target amplification
- Difficult templates
- High-specificity assays
Modified dNTPs for Specialized Molecular Applications
As molecular biology continues to expand into new fields, researchers increasingly require nucleotide analogs beyond standard dATP, dCTP, dGTP, and dTTP.
Modified nucleotides are used in applications such as:
- DNA labeling
- Synthetic biology
- Next-generation sequencing workflows
- Enzymatic DNA synthesis
- Advanced molecular diagnostics
Selecting the appropriate nucleotide chemistry allows researchers to customize PCR performance for specific experimental needs.
Why Choose SBS Genetech dNTPs for PCR?
At SBS Genetech, we understand that nucleotide quality directly affects PCR performance.
From routine amplification to demanding molecular applications, our dNTP products are designed to provide reliable, reproducible results.
High-Purity dNTPs Verified by HPLC
SBS Genetech dNTPs are manufactured under strict quality control standards and verified by HPLC analysis.
High purity helps minimize:
- Degraded nucleotide products
- Reaction variability
- Polymerase inhibition caused by contaminants
This is particularly important for applications requiring high sensitivity and reproducibility.
Nuclease-Free Quality Control
All SBS Genetech dNTP products are tested to ensure the absence of critical contaminants, including:
- DNase
- RNase
This helps protect DNA templates and supports reliable performance in sensitive molecular workflows.
Consistent Formulation and Batch Performance
PCR optimization depends not only on nucleotide identity but also on consistent reagent performance.
Reliable dNTP formulations help researchers achieve:
- Reproducible amplification
- Stable reaction conditions
- Reduced troubleshooting
Applications of SBS Genetech dNTPs
SBS Genetech dNTP products support a broad range of molecular biology applications, including:
PCR and qPCR
Providing the essential nucleotide substrates required for DNA amplification.
RT-PCR
Supporting workflows involving reverse transcription and subsequent DNA amplification.
DNA Sequencing
Providing reliable nucleotide components for sequencing-related applications.
DNA Cloning and Mutagenesis
Supporting accurate DNA construction and modification workflows.
Synthetic Biology
Enabling DNA assembly, engineering, and molecular design applications.
Molecular Diagnostics
Supporting high-performance amplification assays requiring consistent reagent quality.
Frequently Asked Questions About dNTPs in PCR
What is the role of dNTPs in PCR?
dNTPs provide the building blocks required for DNA synthesis during PCR. DNA polymerase uses dATP, dCTP, dGTP, and dTTP to extend primers and generate new DNA copies.
Why are dNTPs required for PCR?
PCR requires dNTPs because DNA polymerase can only synthesize DNA by incorporating deoxynucleoside triphosphates into growing DNA strands.
Without dNTPs, DNA amplification cannot occur.
What concentration of dNTPs is used in PCR?
Most PCR reactions use approximately 0.2 mM of each dNTP, resulting in a total dNTP concentration of about 0.8 mM.
However, optimal concentration depends on polymerase selection, target sequence, and assay requirements.
Can too much dNTP affect PCR?
Yes.
Excessive dNTP concentration can reduce PCR specificity, interfere with magnesium availability, and increase nonspecific amplification.
Can PCR work without dNTPs?
No.
Without dNTPs, DNA polymerase lacks the nucleotide substrates required for DNA strand extension.
Are dNTPs and NTPs the same?
No.
dNTPs are used for DNA synthesis, while NTPs are used for RNA synthesis.
PCR requires dNTPs, not standard NTPs.
What is the difference between dNTP mix and individual dNTPs?
A dNTP mix contains all four nucleotides at balanced concentrations, making it convenient for routine PCR.
Individual dNTP solutions allow researchers to adjust nucleotide ratios for specialized applications.
How should dNTPs be stored?
dNTPs should generally be stored at -20°C for routine use and protected from repeated freeze-thaw cycles.
Which dNTPs are best for PCR?
High-quality dNTPs with high purity, accurate concentration, low nuclease contamination, and consistent batch performance are preferred for reliable PCR results.
Conclusion: Selecting the Right dNTPs for Successful PCR
dNTPs are essential components of PCR because they provide the nucleotide substrates required for DNA synthesis.
The correct balance of dATP, dCTP, dGTP, and dTTP enables DNA polymerase to efficiently amplify target sequences, while optimized dNTP concentration improves amplification efficiency, specificity, and reproducibility.
For most PCR applications, a balanced dNTP concentration of approximately 0.2 mM for each nucleotide provides a reliable starting point. However, advanced workflows such as molecular diagnostics, multiplex PCR, and synthetic biology may require specialized nucleotide formulations and further optimization.
By selecting high-quality, properly formulated dNTP reagents, researchers can minimize experimental variability and achieve more consistent molecular biology results.
SBS Genetech provides a comprehensive range of high-purity nucleotide solutions, including:
- Standard dNTP mixes
- Individual dNTP solutions
- dNTP/dUTP mixes
- Modified nucleotides
- Specialized nucleotide formulations
Designed for applications ranging from routine PCR to advanced biotechnology workflows, SBS Genetech dNTP products help researchers achieve reliable amplification performance and reproducible results.
Explore SBS Genetech’s complete nucleotide portfolio to find the right dNTP solution for your PCR applications.
Featured Citations
Interested in seeing published research using our dNTPs?
Visualized RNA detection of SARS-CoV-2 in a closed tube by coupling RT-PCR with nested invasive reaction
Analyst | 4 Jan 2023 | DOI: https://doi.org/10.1039/d2an01679f
The 20 μL reaction mixtures of the assay contained 1× visualized closed-tube PCR buffer (10 mM Tris–HCl (pH 8.5), 7.5 mM MgCl2·6H2O, 30 mM NaCl, 0.05% NP-40, 0.05% Tween-20), 50 U HiScript II reverse transcriptase, 0.25 mM dNTPs (SBS Genetech Co. Ltd, Beijing, China), 0.5 μM forward primer, 0.5 μM reverse primer, 0.25 U GoTaq DNA polymerase (Promega, Beijing, China), 3.5% PEG8000 (BSK Technology Co. Ltd, Nanjing, China), 0.1 μM UP, 0.4 μM DP, 0.2 μM hairpin probe, 100 ng of FEN1 endonuclease (prepared in our laboratory.
CRISPR/Cas genome editing perspectives for barley breeding
Psysiologia Plantarum | 22 Apr 2022 | DOI: https://doi.org/10.1111/ppl.13686
Primers for sgRNA of eIF4E genes were selected with WhU6 promoter region for amplification of a 362-base pair fragment: F 5′-GACCAAGCCCGTTATTCTGAC-3′, R 5′-AAGTCTGATGCAGCAAGCGAG-3′; for the region including Cas9 with the promoter: F 5′-GCTCCTGGTCCATCCACG-3′, R 5′-CGTG-GATGGACCAGGAGC-3′; for hptII: F 5′-GCTGCGCCGATGGTTTCTACA-3′, R 5′-GCCCAAAGCATCAGCTCATCG. The recommended amplification mixture contained 5 mg of the DNA template (Applied Biosystems); 2.5 mM MgCl2; 250 μM dNTPs (Beijing SBS Genetech Co., Ltd.)
Femtomolar and locus-specific detection of N6-methyladenine in DNA by integrating double-hindered replication and nucleic acid-functionalized MB@Zr-MOF
Journal of Nanobiotechnology | 7 Dec 2021 | DOI: https://doi.org/10.1186/s12951-021-01156-0
Klenow Fragment DNA polymerase (3′ → 5′ exo−), 10 × Klenow buffer (500 mM Tris–HCl, 50 mM MgCl2 and 10 mM DTT, pH 7.9), and 10 × CutSmart™ buffer (20 mM Tris–acetate, 500 mM potassium acetate, 10 mM magnesium acetate and 100 µg/mL BSA, pH 7.9) were obtained from New England Biolabs (Beijing, China). GoldView I, 20 bp DNA marker, and dATPs, dTTPs, dCTPs and dGTPs were purchased from SBS Genetech Co., Ltd., (Beijing, China)
Multiplex Visualized Closed-Tube PCR with Hamming Distance 2 Code for 15 HPV Subtype Typing
Anal. Chem. | 22 Mar 2021 | DOI: https://doi.org/10.1021/acs.analchem.1c00035
Reagents included GoTaq Hot Start Polymerase (Taq DNA polymerase) (Promega), flap endonuclease 1 (FEN1) prepared in our laboratory as described previously, (19) deoxynucleotide triphosphates (dNTPs) (SBS Genetech Co., Ltd., China)
An integrated electrochemical biosensor based on target-triggered strand displacement amplification and “four-way” DNA junction towards ultrasensitive detection of PIK3CA gene mutation
Biosensors and Bioelectronics | 15 Feb 2020 | DOI: https://doi.org/10.1016/j.bios.2019.111954
NsbI restriction enzyme, Klenow Fragment (KF) (3′→5′exo-), Nb.BbvCI, 10 × Klenow buffer (500 mM Tris-HCl, 50 mM MgCl2 and 10 mM DTT, pH 7.9) and 10 × CutSmart™ buffer (20 mM Tris-acetate, 500 mM potassium acetate, 10 mM magnesium acetate and 100 μg/mL BSA, pH 7.9) were obtained from New England Biolabs (Beijing, China). GoldViewⅠ, DNA marker and dNTP were purchased from SBS Genetech Co., Ltd (Beijing, China)
Sequence-encoded quantitative invader assay enables highly sensitive hepatitis B virus DNA quantification in a single tube without the use of a calibration curve
Royal Society of Chemistry | 8 Aug 2019 | DOI: https://doi.org/10.1039/c9an00970a
A virus RNA/DNA Extraction Kit was purchased from Xi'an Tianlong Science and Technology Co., Ltd (Xi'an, China), deoxynucleotide triphosphates (dNTPs) were obtained from SBS Genetech Co., Ltd (Beijing, China)
Dual cycle amplification and dual signal enhancement assisted sensitive SERS assay of MicroRNA
Analytical Biochemistry | 1 Jan 2019 | DOI: https://doi.org/10.1016/j.ab.2018.10.004
Klenow fragment of E.coli DNA polymerase and nicking endonuclease (NEase) were purchased from Thermo Fisher Scientific Inc. (Waltham, MA, USA). BEAS-2B cells was purchased from GeFan Biotechnology.Go.,Ltd (Shanghai, China). Cell lysis buffer was purchased from Sangon Biotech (Shanghai, China). The mixture of four dNTPs (10 mM for each component) was purchased from SBS Genetech Co., Ltd. (Beijing, China).